Functional nerve stimulation (FNS) can restore lost function in patients with damaged nervous system as in spinal cord injury or stroke. Electrodes placed directly on the nerves offer many advantages over muscular stimulation, including control of several muscles with one device, low power requirements, and the potential for recording afferent neural signals. Progress in this area, however, has been hampered by the lack of a truly safe and selective electrode for stimulation of, and recording from, peripheral nerves. In the previous grant application cycle, a novel type of electrode has been developed. This electrode either reshapes a nerve into a flat configuration or maintains it in an already flat shape. This Flat Interface Nerve Electrode (FINE) can both selectively record and stimulate nerves and studies have shown that it can be safe. In this competing renewal, we propose to capitalize on the advantage provided by the ability to line-up the fascicles and to get electrical contacts close to every axon within the nerve. This study has been divided into five primary objectives. The first objective is to determine the effect of the rate of reshaping of the nerve on the safety of the electrode. Hybrid electrodes designs that combine silicone with biodegradable polymer can provide a slow rate of reshaping of the electrode and will be implanted in animals. The second aim focuses on the ability of the fine with contacts arrays positioned along the nerve to activate selectively fibers with specific diameters. The capability to restore normal recruitment by selectively activating small fibers and then large fivers is crucial to the success of neuroprosthetics devices. The third aim is to show that the fine electrode can differentiate neural activity from individual fascicles. Blind sources separation algorithms will be used to obtain the fascicular source activity from the voltage obtained at electrode contacts. The fourth aim is to determine the optimal contact configuration for selective stimulation. Computer models and animal's experiments will be combined to determine the optimum design in both animal and human nerves. Finally, the last aim is to implement an optimal wireless design of the Flat Interface Nerve Electrode (FINE). A 32-channel peripheral nerve electrode will be built by embedding an electronic circuit within a silicone cuff with only two external leads to a battery pack. The control of the stimulation parameters and the charging of the battery will be done by wireless control. The end product of this project will be a peripheral nerve electrode consisting of a wireless electrode for selective neural stimulation and recording and capable of fiber diameter control. This electrode could significantly improve the ability of current neural prosthetic devices to restore neuromuscular function.